1. Field of the Invention
The present invention generally relates to a catalyst for treating exhaust gas and a method for producing the same, and more particularly to a catalyst for treating an exhaust gas containing carbon monoxide and volatile organic compounds and a method for producing the catalyst for treating the exhaust gas.
2. Description of the Related Art
Exhaust gases discharged from various industrial equipment such as automobile engines, gas engines, gas turbines for aircraft and for power generation, and equipment in chemical plants and in various factories contain NOx, SOx, CO (carbon monoxide), unburned volatile organic compounds (VOCs), and the like. Catalysts for treating exhaust gas are used for treating such substances contained in exhaust gas.
For example, Japanese Patent Laid-Open No. 10-309462 discloses a NMHC oxidation catalyst in which Pt (platinum) is supported on an alumina carrier.
However, such a catalyst for treating exhaust gas in which Pt (platinum) is supported on an alumina carrier is excellent in removing CO and VOCs based on unsaturated hydrocarbons such as C2H4 but is poor in removing saturated hydrocarbons such as C3H8.
It is desired to remove not only CO and VOCs based on unsaturated hydrocarbons such as C2H4 but also to improve the removal of saturated hydrocarbons such as C3H8 (propane). For example, an exhaust gas from gas turbines may contain about 5 ppm of unsaturated hydrocarbons such as C2H4 and about 2 ppm of saturated hydrocarbons such as C3H8. VOC emission control is not established yet in Japan but already established in some foreign countries. For example, according to U.S. VOC emission control, the emission of VOCs is restricted to 2 ppm or less. Even if 90% of unsaturated hydrocarbons can be reduced, a saturated hydrocarbon-emission concentration needs to be reduced by at least 25%, from 2 ppm to 1.5 ppm. Similarly, the emission of CO (carbon monoxide) is also restricted. For example, it is restricted to 2 ppm or less in United States. Since the emission concentration of CO discharged from a gas turbine may exceed 60 ppm, 97% or more of the exhaust gas needs to be reduced.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a catalyst for treating exhaust gas adapted not only to remove CO and VOCs based on unsaturated hydrocarbons such as C2H4 but also to accelerate the decomposition reaction of saturated hydrocarbons such as propane and to provide a method for producing such a catalyst for treating exhaust gas.